Mr(K2S) = 2*39+32=110
Mr(K) =39
Mr(S)=32
w(K) = 2*39/110*100%=70.91%
w(S)=32/110*100%=29.09%
Mr(Na2CO3) =2*23+12+16*3=106
Mr(Na) =23
Mr(C)=12
Mr(O)=16
w(Na) = 46/106*100%=43.4%
w(C)=12/106*100%=11.3%
w(O)=48/106*100%=45.3%
Mr(Al2S3) = 2*27+3*32=150
w(Al) = 54/150=0.36